Expert: Bruce E. Johnson - 3/1/2009

Question
Bruce-- We have a barn with a 10 foot ceiling.  We want to have a set of stairs (not folding) to get to the loft. We want something we can pivot the bottom up to the ceiling out of the way.  (we'd use a counterbalance to be able to handle the weight.)  The total rise is 10', the total run would be 10' and the length of the 'step/ladder' is 14' with 45' angle....   Is there any good way to attach/suspend a staircase so it would pivot and be safe from falling?  I could send a sketch if it would help...

Answer
Hi Ken, a lot can be learned from looking at the drop down attic ladders you can find at home improvement stores.  They use a coil spring system that locks into place when pulled down and they release and pull up when lifted.  The key is to weigh the stair assembly you want to use.  Then it is relatively easy to determine the counterweight required for "negative bouyancy".  It should require 20-40 pounds of pull to lower the assembly.  So if your stairs weigh 200 pounds you will need 220-240 pounds of lift either with the counterweight pulley system, hydraulic or  spring  system.  Most springs and hydraulic arms have a rating in pounds.  You will need to find two, one for each side of the unit that will add up to the desired uplift.  Pulleys and cables are a little more difficult to figure because a pulley will reduce the weight based on the size of the pulley.  Honestly I haven't built a drop down stair before.  I have built five theaters with fly towers and counterweighted light bars and flying scenery bars.  With a counter weight system you can build the stair in place and then attach the cables to each side and the pulleys above.  Then you can load the cable with the counter weight until the stair lifts to its closed position.  It is a trial and error method but easier than trying to estimate spring size and other data.  Keeping the stair locked in place can be as simple as using a gate lock that can be released with a cord pull or as I said earlier using 20-40 pounds over so that much pull will be required to lower the system.  Then you may need a simple lock at the floor to keep it from raising on its own.  I hope this information helps feel free to write again regarding this or other matters sincerely bruce e johnson..bejohnsonconsulting.com